is article presents a rational choice account of Brazil's jogo do bicho ("animal game"), possibly the largest illegal lo ery game in the world. In over 120 years, the jogo do bicho has grown from a local ra e to a multimillion-dollar business, and the game has played a major role in Brazil's cultural and political life. My analysis of the jogo do bicho has three goals. First, I examine the mechanisms that fostered the lo ery's notable growth outside the boundaries of Brazilian law. Second, I investigate how the animal game nanciers combine costly signals and selective incentives to induce cooperation from members of the community. Lastly, I discuss the relationship between the lo ery sponsors and Brazilian representatives, particularly how the bicheiros exploit the fragmentation of Brazil's political system to advance their long-term interests.